Energy saving of an automobile air-conditioning system appears to be quite important as the requirement for the automobile energy saving becomes increasingly higher. In a conventional automobile air-conditioning system, a throttle mechanism generally includes a thermal expansion valve and a throttling short tube. Compared to the conventional throttle mechanism, the electronic expansion valve has a relatively strong advantage in overheat control and overall energy saving since the electronic expansion valve may realize an accurate control.
However, there are some limitations for the application of the electronic expansion valve in the automobile air conditioner, and one main factor is that the electronic expansion valve is an electric component and is difficult to meet a requirement for temperature resistance of the automobile environment. An overly high operating environment temperature may burn and damage the coil of the electronic expansion valve and the control chip, thus the electronic expansion valve cannot work normally, which may in turn affect the operation of the whole air-conditioning system. In order to enhance the level of the temperature resistance of the electronic expansion valve, the volume of the electronic expansion valve must be increased, however the increased volume may not only increase the cost, but also fail to show the application advantages of the electronic expansion valve.
At present, due to the price factor and the technical bottleneck of the electronic expansion valve, the thermal expansion valve is also applied in the new energy automobile air conditioner as well as the conventional gasoline car. Due to influences from factors of weather, road condition, thermal load, engine speed and etc., an automobile air conditioner generally works under a non-standard design working condition. However, the set value of an overheat degree of the thermal expansion valve is set according to a standard working condition. When the system is operated under a non-standard working condition, the overheat degree tends to deviate from the set value of the overheat degree, thereby causing the decrease of the system efficiency and an unstable operation, and causing dew formation or even frost formation on the evaporator under a certain condition.
In an air-conditioning system of an electric automobile, an electronic expansion valve is required to cooperate with a varying speed adjustment of a variable volume electrical compressor. Especially, the electrical compressor works independently in the air-conditioning system of the electric automobile, which is different from that in the gasoline car that the compressor is driven by an engine belt pulley. However, a flow adjusting characteristic of the thermal expansion valve cannot be combined with a frequency conversion characteristic of the electrical compressor, which results in a large power load, and a low travel distance per charge of the electric automobile.
Therefore, the application of the electronic expansion valve in the automobile air-conditioning field appears to be extremely important.